"I want to express what I think is a widely shared sentiment today, both by way of gratitude and commendation for your work. We don't have time today to do a full listing of all the achievements that you should get credit for," the U.S. senator gushed. He praised the Secretary of State's work on reducing the flow of an IED chemical into Afghanistan, her international women's rights efforts and her overall humanitarian assistance.

Clinton responded in kind, "Let me thank you for those three topics you covered, and particularly your very clear focus on the IED problem and the ammonium nitrate problem in Pakistan. You and I have talked about this. You've gone there, I've gone there and carried that message and I thank you for making it an issue."

Casey, the Foreign Relations chairman of the subcommittee that oversees Libya, asked Clinton how Congress could be of assistance helping the State Department implement recommendations of a review board that investigated the events surrounding the Sept. 11, 2012 embassy attack that killed four Americans, including the U.S. ambassador. The in-house board outlined a list of security failures in a report released in mid-December.

The outgoing secretary urged Casey and the committee to continue to hold the State Department accountable on taking the corrective steps. In her testimony, Clinton said 85 percent of the board’s suggestions are "on track to be completed by the end of March."

She also asked for support on budgetary needs - she noted at another point in the hearing that funding shortfalls have made it difficult for the department to fund security needs abroad.

In concluded answering Casey's question, Clinton said she had wanted the board's analysis out in the open. "I want to know more than anybody what happened. Don't hold any punches. Tell us what the facts are," she said.

"But," she added, "now we have to act on it, or shame on us."

For more on Clinton's Senate appearance, the Washington Post has a highlight reel of its most memorable moments. Watch here.